1. Field of the Invention
The invention relates to a mending and test method, and more particularly to a method of mending and testing a semiconductor apparatus.
2. Description of the Related Art
Due to the very small dimensions, conventional memory products, such as static random access memories (SRAM) and a dynamic random access memories (DRAM), do not always operate normally. To avoid this, a laser mending machine is used to scan two L-shaped or T-shaped laser targets on the devices. The damaged circuits are then found and mended.
As process techniques grow more and more advanced, the dimension of devices becomes smaller and smaller. As the laser target further shrinks, or the circuit is designed too close to the laser target, the laser mending machine can not correctly recognize the circuit to be mended, and therefore, the mending efficiency and the yield of devices is degraded.
A rectangular diagram of a mending and testing method using an L-shaped laser target, and the L-shaped laser target are shown in FIG 1a and FIG. 1b.
Referring to FIG. 1a, on a wafer, the device 10 to be mended is found. Two L-shaped laser targets (12 and 14) are formed on the device 10. Referring to FIG. 1b, an enlarged view of the L-shaped laser target 12 is shown. On the L-shaped laser target 12, there are an X-coordinate 16 and a Y-coordinate 18. The outer lengths for both X axis and Y axis are both about 40 .mu.m, and the thickness is about 5 .mu.m. The dimension of the other L-shaped laser target 14 is similar to the laser target 12. The X-coordinate and the Y-coordinate for both laser targets 12 and 14, are pre-set before the process. Therefore, using a laser mending machine to scan and find the positions of the X-coordinate and the Y-coordinate, the relative address of the damaged circuit is defined, and the position of the damaged circuit 8 (as shown on FIG. 1a) can be found. The fuse of the damaged circuit is then blown by the laser mending machine, and a new circuit with the same function is disposed to enable the device to operate normally.
A rectangular diagram of a mending and testing method using a T-shaped laser target, and the T-shaped target, are shown as FIG. 2a and FIG. 2b.
Referring to FIG. 1a, on a wafer, the device 20 to be mended is found. Two sets of T-shaped laser target, are found (22 and 24 are the first set, 26 and 28 are the second set) on the device 20. Referring to FIG. 2b, an enlarged view of the T-shaped target set 22 and 24 is shown. The laser target 22 is a longitudinal bar with an X-coordinate 32, and the laser target 24 is a transverse bar with a Y-coordinate 34. The length and the width of the longitudinal bar shaped laser target 22 is 40 .mu.m and 5 .mu.m, respectively, whereas the length and the width of the transverse bar-shaped laser target 22 is 5 .mu.m and 40 .mu.m, respectively. The other target set of laser targets 26 and 28 is similar to the set 22 and 24. The X-coordinates and the Y-coordinates for both target sets 22 and 24, and 26 and 28 are pre-set before the process. Therefore, using a laser mending machine to scan and find the positions of X-coordinates and the Y coordinates, the relative address of the damaged circuit is defined, and the position of the damaged circuit 30 (as shown on FIG. 2a) can be found. The fuse of the damaged circuit is then blown by the laser mending machine, and a new circuit with the same function is disposed to enable the device to operate normally.
As the technique is improved, the space for devices becomes smaller. However, the dimension of the laser target to be recognised by a laser mending machine cannot be reduced, otherwise, misalignment and misjudgement are very likely to happen. The large space occupied by the laser target causes the circuit in the device to be very close to the laser target. The misalignment and misjudgement are again, very likely to happen. Therefore, the mending efficiency of the laser mending machine and the yield of the devices is degraded. On the other hand, if there is any mistake of the data of coordinate supplied by product engineers or design engineers, the mending effect is affected.